Cationic starch as a precursor to prepare porous activated carbon for application in supercapacitor electrodes

Three activated carbons (ACs) for the electrodes of supercapacitor were prepared from cationic starch using KOH, ZnCl2 and ZnCl2/CO2 activation. The BET surface area, pore volume and pore size distribution of the ACs were evaluated using density functional theory method, based on N-2 adsorption isotherms at 77K. The surface morphology was characterized with SEM. Their electrochemical performance in prototype capacitors was determined by galvanostatic charge/discharge characteristics and cyclic voltammetry, and compared with that of a commercial AC, which was especially prepared for use in supercapacitors. The KOH-activated starch AC presented higher BET surface area (3332 m(2) g(-1)) and larger pore volume (1.585 cm(3) g(-1)) than those of the others, and had a different surface morphology. When used for the electrodes of supercapacitors, it exhibited excellent capacitance characteristics in 30wt% KOH aqueous electrolytes and showed a high specific capacitance of 238 Fg(-1) at 370 mAg(-1), which was nearly twice that of the commercial AC. (C) 2008 Elsevier Ltd. All rights reserved.